1. Technical Field
The present invention relates to a water resistant aluminum pigment dispersion, an aqueous ink composition containing the same, and a method for manufacturing a water resistant aluminum pigment dispersion.
2. Related Art
Heretofore, as a method for forming a coating film having a metallic gloss on a printed material, for example, a method using a printing ink in which a gold powder or a silver powder formed, for example, from a brass or an aluminum fine powder is contained as a pigment, a foil press printing method using a metal foil, or a thermal transfer method using a metal foil may be mentioned.
In recent years, many applications of ink jet techniques have been performed in printing fields, and as one of the applications, metallic printing may be mentioned, so that development of an ink having a metallic gloss has been carried out. For example, in JP-A-2008-174712, an aluminum pigment dispersion containing an organic solvent, such as an alkylene glycol, as a basic component and a non-aqueous ink composition containing the above dispersion have been disclosed.
On the other hand, in views of global environmental conservation, safety for human beings, and the like, instead of a non-aqueous ink composition containing an organic solvent as a basic component, development of an aqueous ink composition has been actually desired. However, when an aluminum pigment is dispersed in water, it generates a hydrogen gas and also forms alumina by a reaction with water, and whitening occurs thereby. As a result, in the aluminum pigment, its metallic gloss may be disadvantageously degraded in some cases.
Accordingly, for example, in JP-A-2004-131542, a technique has been disclosed in which after the surface of an aluminum pigment is covered with a hydrolysis-condensation product containing a siloxane bond, the aluminum pigment is dispersed in water or an aqueous solvent containing a surfactant.
However, when an aluminum pigment provided with siloxane bonds on the surface thereof is dispersed in an aqueous solvent, particles of the aluminum pigment may agglomerate with each other, and/or a metallic gloss of the aluminum pigment may be degraded in some cases due to the agglomeration.